No, David killed them all a few years later.

And David and his men went up, and invaded the Geshurites, and the Gezrites, and the Amalekites: for those [nations were] of old the inhabitants of the land, as thou goest to Shur, even unto the land of Egypt.

And David smote the land, and left neither man nor woman alive, and took away the sheep, and the oxen, and the asses, and the camels, and the apparel, and returned, and came to Achish.

And then David killed them all again, just to make sure. (Except this time 400 guys escaped.)

No, Saul was killed by an Amalekite.

And he said unto me, Who [art] thou? And I answered him, I [am] an Amalekite.

He said unto me again, Stand, I pray thee, upon me, and slay me: for anguish is come upon me, because my life [is] yet whole in me.

So I stood upon him, and slew him, because I was sure that he could not live after that he was fallen: and I took the crown that [was] upon his head, and the bracelet that [was] on his arm, and have brought them hither unto my lord.